1. Field of the Invention
The present invention relates to a monolithic integrated interdigital coupler comprising a plurality of parallel side-by-side conductors and, more particularly, to a monolithic integrated interdigital coupler including a plurality of parallel side-by-side conductors, wherein the end of each conductor is connected with a conductor not immediately adjacent to it by means of a conducting air bridge.
2. Prior Art
This type of inter digital coupler, which is often called a "Lange-coupler" in the literature, is disclosed in the textbook, "Integrated Microwave Circuitry (Integrierte Mikrowellenschaltungen)", by R. K. Hoffmann, Springer-Verlag, 1983, pp. 260 to 262. A very close or tight coupling can be obtained with an interdigital circuit structure. When an interdigital coupler is to be monolithically integrated, the conductor widths and distances between the conductors must be less than 8 .mu.m in order for example to obtain good electrical properties. This type of small conductor strip and spacing between the conductor are however very difficult to obtain with state of the art circuit technology. Thus if a monolithic integrated interdigital coupler of the above-described type is to be made easily, even with larger conductor widths and larger distances between the conductors, a very high degree of coupling must be achieved.